i haven't been able to come up with any info on this. specifically, i have a .264 video i need to mux with a 5.1 wav file into an mp4 container. can this be done? i use gpac and mp4box to do this with simple stereo but i have to convert the audio to m4a first. what would be the best way, using my existing tools, if possible, to get the best quality mp4/5.1 surround from my elements? i have many tools including: gpac mp4box x264 ffmbc mpegstreamclip final cut v5 thanks for any help, BabaG